body {
  margin: 0px;
}

.container {
  display: flex;
  flex-wrap: wrap;
}
.container > div {
  width: 25%;
}
/* if(screen<=768px) */
@media screen and (max-width: 768px) {
  .container > div {
    width: 100%;
  }
}
/* if(screen>=769px && screen<=1000px) */
@media screen and (min-width: 769px) and (max-width: 1000px) {
  .container > div {
    width: 50%;
  }
}
@media screen and (min-width: 1001px) and (max-width: 1366px) {
  .container > div {
    width: 33.333333333%;
  }
}

/* 媒体查询的意义就是在不同分辨率下可以有不同样式 */
.desktop {
  display: block;
}
.phone {
  display: none;
}

@media screen and (max-width: 768px) {
  .desktop {
    display: none;
  }
  .phone {
    display: block;
  }
}
